We are starting FoF and I wanted to begin to prep for forther sessions.

Another question. After Lords of oblivion it says the PC's learn the history of Vhalantru. I cannot seem to find it.

No I never did but my group will be playing that adventure very soon so I will be forced too. I may just use the outline I created and run with it from there. I'll need to revisit the adventure itself and see if where I need to flesh it out and add stats, treasure, villain strategies etc. I'll get back to you though.

Here is the history you can find in the document 'Adimarchus and the New Cagewrights' -

For hundreds of years Adimarchus lead the great celestial armies of heaven against the demonic hordes of the Abyss and in particular, the dark armies of the demon lord Graz’zt.

Adimarchus was cast from the heavens for a crime of love and pride. He was forbidden to descend the mountain to seek the love of a lesser angel. When his deception was revealed and a troop of angels attempted to capture the two. When one angel harmed his love, Adimarchus lashed out in anger slaying the guard before finally being restrained.

In the Cathedral of Feathers Adimarchus was sentenced to the greatest punishment that could be possibly given to an angel – banishment.
For Adimarchus this sentence was worse than death for he was not only cast from heaven but worst still he was torn from his greatest love - Nidrama. This loss was too much for the fallen angel to bear and he was determined to return to the Seven Mounting Heavens are reclaim Nidrama at any cost.

Adimarchus was so blinded by his love for Nidrama that he sought the aid of his ultimate enemy - Graz’zt, whose demonic forces he had lead celestial armies against for hundreds of years. The irony delighted the evil lord and he agreed to award Adimarchus command of his greatest army and greatest general...Occiptus.

Graz’zt tore from the angel part of his soul and in return placed part of Occiptus’ soul within him – forever linking the two, demon and angel.
When Adimarchus’ invasion of heaven failed so did his hope of reuniting with his love and the demonic part of his soul began to feed upon his despair, his Inner Demon started to slowly control him and the two parts of Adimarchus formed.

Now locked in his cage, Adimarchus is lost to his despair and has become insane from his betrayal. Within his maddening nightmares, Adimarchus’ Inner Demon reaches out across Canceri and into the Material Plane to corrupt and control.

One of the first to be touched by Adimarchus’ madness and was eventually corrupted by his Inner Demon, was a powerful demodand called Dry’yrd. Adimarchus’ Inner demon realized that if he could engineer Adimarchus escape he could completely destroy the angels mind and assume complete control of the celestial forever.